The present invention relates generally to machine tools and more particularly, to a process and apparatus for minimizing dust production and for the removal of chip material at the machining station of a machine tool during the machining of workpieces. Even more specifically, the present invention relates to the machining of workpieces made from graphite in which a fluid is supplied to the machining point and this serves to trap the graphite dust which is combined with the fluid and is removed together with the chips from the machining point, as well as to an apparatus for performing this process.
It is known that, during the machining of workpieces from particular materials, there is a considerable production of dust, which is not only unpleasant and prejudicial to the health of the workers, but also leads to stoppages of the machines and to the contamination of the working area. Such a material is, for example, graphite, which is used in the production of a great variety of electrode types for use on spark erosion machines. Graphite workpieces are appropriately shaped by machining, e.g. by milling.
For the protection of workers and machines against the suspended dust produced when working graphite, it is known to use transparent covering hoods. However, as workpieces with the most varied shapes are produced, the hoods must be adapted to the workpieces individually. Even so, the hoods impede vision and the working space. In addition, the constantly changing of the movement tool and particularly in vertical movement, permits no fixed covering between tool and workpiece without creating a considerable accidental risk. The use of elastic covers, e.g. elastic hoods, is also ineffective in reducing the aforementioned disadvantages.
To improve this known process, another process is known, which is particularly used in the dry working of graphite workpieces. Strong industrial vacuum cleaners are used for sucking up chips and dust produced in the vicinity of the working station, e.g. at the point of action of the milling cutter. However, the constantly changing interaction of the tool or cutter with the workpiece during working makes a satisfactory removal thereof impossible. In addition, the voluminous suction lines with the suction nozzle obstruct the working area. Moving the suction nozzle by hand does not represent a satisfactory solution and also increases risks of injury. In the case of multiple spindle machines, this type of dust removal becomes even more problematic due to the resulting considerable expenditure on material and space. If additional suction hoods are used, their efficiency decreases considerably and conventional suction or exhausting equipment is no longer adequate, so that rooms and work areas become even dustier.
It is also known to replace the aforementioned dry working or machining, which suffers from the aforementioned disadvantages, by wet working or machining. As coolant means are always provided on the machining equipment, it is obvious to use these for suppressing dust production, it merely being necessary to change the cooling fluid. Although in this way a large part of the chips can be combined with the coolant, this process is still unable to prevent the formation of suspended dust. It is particularly disadvantageous that the coolant circuit incorporated into the machine is made dirty by the dust and chips produced during cutting. The cleaning of the machine after working constitutes a time-consuming activity and the black, dirty sludge produced when machining graphite workpieces can only be removed from the machine with considerable effort and expenditure. The machine and the work areas remain coated with a layer of black dust, which can only be removed with considerable effort.